Some conventionally known vehicle lighting units to be installed on a vehicle body can include those capable of emitting light rays in an elongated line shape by means of a light guiding bar that has a relatively simple configuration.
However, the use of the light guiding bar may possess difficulty in accurate light distribution control, resulting in reduction of the light utilization efficiency. In addition, since the light incident face of such a light guiding bar in front of which a light source can be disposed is essentially limited to both end faces in the longitudinal direction. This configuration makes it difficult to obtain brighter light with high intensity.
Therefore, when light with high intensity is required, a light guiding lens capable of controlling light distribution with higher accuracy than the light guiding bar is used instead.
In general, such a light guiding lens of a so-called diffusion type can be configured to have a recessed light incident face for receiving light from a light source to diffuse the received light in the lengthwise direction.
Further, another known light guiding lens can have a convex face at the center thereof in front of the light source, and the entering light rays can be made parallel by the convex face. The light guiding lens can further have side faces on both sides of the convex face where the entering light rays can be guided to total reflection faces to be totally reflected forward. Such a total-reflection type light guiding lens is disclosed, for example, Japanese Patent Application Laid-Open No. 2013-257947.
Recent trend of light sources for use in vehicle lighting unit includes the application of a light emitting diode (LED) excellent in environmental performances. LEDs can generally have a directivity in which the light intensity thereof is decreased as the emission angle becomes large, thereby emitting high intensity light designed around its optical axis at its front center.
Under such a circumstance, when such an LED is used in the system including the conventional diffusion type or total-reflection type light guiding lens, the high intensity light rays emitted from an LED around its optical axis cannot be properly controlled. As a result, the portion of a light emission face just in front of the LED may be brighter than the other portion, resulting in luminance unevenness.